U.S. patent application number 12/300423 was filed with the patent office on 2009-05-07 for thermally stable aluminum trihydroxide particles produced by spray drying with subsequent dry-milling and their use.
This patent application is currently assigned to Martinswerk GmbH. Invention is credited to Ingo Uwe Heim, Rene Gabriel Erich Herbiet, Volker Ernst Willi Keller, Dagmar Linek, Norbert Wilhelm Puetz, Winfried Toedt.
Application Number | 20090118410 12/300423 |
Document ID | / |
Family ID | 38833827 |
Filed Date | 2009-05-07 |
United States Patent
Application |
20090118410 |
Kind Code |
A1 |
Herbiet; Rene Gabriel Erich ;
et al. |
May 7, 2009 |
Thermally Stable Aluminum Trihydroxide Particles Produced By Spray
Drying With Subsequent Dry-Milling and Their Use
Abstract
The present invention relates to a novel process for the
production of aluminum hydroxide flame retardants having improved
thermal stability, the aluminum hydroxide particles produced
therefrom, the use of the aluminum hydroxide particles produced
therefrom in flame retarded polymer formulations, and molded or
extruded articles made from the flame retarded polymer
formulations.
Inventors: |
Herbiet; Rene Gabriel Erich;
(Eupen, BE) ; Keller; Volker Ernst Willi;
(Frechen, DE) ; Linek; Dagmar; (Cologne, DE)
; Toedt; Winfried; (Steffeln-Auel, DE) ; Puetz;
Norbert Wilhelm; (Niederaussem, DE) ; Heim; Ingo
Uwe; (Frechen, DE) |
Correspondence
Address: |
ALBEMARLE CORPORATION;PATENT DEPARTMENT
451 FLORIDA STREET
BATON ROUGE
LA
70801
US
|
Assignee: |
Martinswerk GmbH
Bergheim
DE
|
Family ID: |
38833827 |
Appl. No.: |
12/300423 |
Filed: |
June 21, 2007 |
PCT Filed: |
June 21, 2007 |
PCT NO: |
PCT/IB2007/002314 |
371 Date: |
November 11, 2008 |
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Current U.S.
Class: |
524/437 ;
423/629 |
Current CPC
Class: |
C01F 7/02 20130101; C01P
2004/62 20130101; C08K 9/02 20130101; C09C 1/407 20130101; C01P
2006/80 20130101; C01F 7/021 20130101; H05K 1/0373 20130101; C01P
2006/16 20130101; C01F 7/18 20130101; Y10T 428/2982 20150115; C01P
2006/14 20130101; C09C 1/02 20130101; C08K 3/22 20130101; C01P
2002/88 20130101; C01P 2006/12 20130101; C01F 7/023 20130101; C01P
2006/40 20130101; C09K 21/02 20130101; C01P 2006/19 20130101; C01P
2004/61 20130101 |
Class at
Publication: |
524/437 ;
423/629 |
International
Class: |
C08K 3/22 20060101
C08K003/22; C01F 7/02 20060101 C01F007/02 |
Claims
1-25. (canceled)
26. A process for producing dry-milled ATH particles comprising: a)
spray drying an aluminum hydroxide slurry or filter cake containing
in the range of from about 1 to about 85 wt. % ATH, based on the
total weight of the slurry and/or filter cake, to produce
spray-dried aluminum hydroxide particles; and b) dry milling said
spray dried aluminum hydroxide particles thus producing dry-milled
ATH particles, wherein the dry-milled ATH particles have a
V.sub.max in the range of from about 300 to about 700 mm.sup.3/g
and/or an r.sub.50 in the range of from about 0.09 to about 0.33
.mu.m, and one or more of the following characteristics: i) a
d.sub.50 of from about 0.5 to about 2.5 .mu.m; ii) a total soda
content of less than about 0.4 wt. %, based on the total weight of
the dry-milled ATH particles; iii) an oil absorption of less than
about 50%, as determined by ISO 787-5:1980; and iv) a specific
surface area (BET) as determined by DIN-66132 of from about 1 to
about 15 m.sup.2/g, wherein the electrical conductivity of the
dry-milled ATH particles is less than about 200 .mu.S/cm, measured
in water at 10 wt. % of the ATH in water.
27. The process according to claim 26 wherein said slurry or filter
cake is obtained from a process that involves producing ATH
particles through precipitation and filtration.
28. The process according to claim 26 wherein said slurry or filter
cake is obtained from a process that comprises: a) dissolving
aluminum hydroxide in caustic soda to form a sodium aluminate
liquor; filtering the sodium aluminate solution to remove
impurities; cooling and diluting the sodium aluminate liquor to an
appropriate temperature and concentration; adding ATH seed
particles to the sodium aluminate solution; allowing ATH particles
to precipitate from the solution thus forming an ATH suspension
containing in the range of from about 80 to about 160 g/l ATH,
based on the suspension; filtering the ATH suspension thus forming
said filter cake, and optionally washing said filter cake one or
more times with water before it is spray dried; or, b) dissolving
aluminum hydroxide in caustic soda to form a sodium aluminate
liquor; filtering the sodium aluminate solution to remove
impurities; cooling and diluting the sodium aluminate liquor to an
appropriate temperature and concentration; adding ATH seed
particles to the sodium aluminate solution; allowing ATH particles
to precipitate from the solution thus forming an ATH suspension
containing in the range of from about 80 to about 160 g/l ATH,
based on the suspension; filtering the ATH suspension thus forming
a filter cake; optionally washing said filter cake one or more
times with water before it is re-slurried; and re-slurrying said
filter cake to form a slurry comprising in the range of from about
1 to about 85 wt. % ATH, based on the total weight of the
slurry.
29. The process according to claim 26 wherein the BET of the ATH
particles in the slurry or filter cake is a) in the range of from
about 1.0 to about 4.0 m.sup.2/g or b) in the range of from about
4.0 to about 8.0 m.sup.2/g, or c) in the range of from about 8.0 to
about 14 m.sup.2/g; and/or wherein the ATH particles in the slurry
or filter cake have a d.sub.50 in the range of from about 1.5 to
about 3.5 .mu.m.
30. The process according to claim 29 wherein said slurry or filter
cake contains i) in the range of from about 1 to about 85 wt. % ATH
particles; ii) in the range of from about 25 to about 70 wt. % ATH
particles; iii) in the range of from about 55 to about 65 wt. % ATH
particles; in the range of from about 40 to about 60 wt. % ATH
particles; iv) in the range of from about 45 to about 55 wt. % ATH
particles; v) in the range of from about 25 to about 50 wt. % ATH
particles; or vi) in the range of from about 30 to about 45 wt. %
ATH particles; wherein all wt. % are based on the total weight of
the slurry or the filter cake.
31. The process according to any of claims 26 or 29 wherein the ATH
particles in the slurry or filter cake have: a) a total soda
content of: i) less than about 0.2 wt. %, based on the ATH
particles in the slurry or filter cake; or ii) less than about 0.1
wt. %, based on the ATH particles in the slurry or filter cake;
and/or b) a non-soluble soda content in the range of from about 70
to about 99.8% of the total soda content, with the remainder being
soluble soda.
32. The process according to claim 26 wherein said slurry or filter
cake comprises a dispersing agent.
33. The process according to claim 26 wherein said dry-milled ATH
particles are classified or treated in one or more pin mills.
34. The dry-milled ATH particles according to claim 26.
35. Dry-milled ATH particles having a V.sub.max in the range of
from about 300 to about 700 mm.sup.3/g and/or an r.sub.50 in the
range of from about 0.09 to about 0.33 .mu.m, and one or more of
the following characteristics: i) a d.sub.50 of from about 0.5 to
about 2.5 .mu.m; ii) a total soda content of less than about 0.4
wt. %, based on the total weight of the dry-milled ATH particles;
iii) an oil absorption of less than about 50%, as determined by ISO
787-5:1980; and iv) a specific surface area (BET) as determined by
DIN-66132 of from about 1 to about 15 m.sup.2/g, wherein the
electrical conductivity of the dry-milled ATH particles is less
than about 200 .mu.S/cm, measured in water at 10 wt. % of the ATH
in water.
36. The dry-milled ATH particles according to claim 35 wherein said
dry-milled ATH particles have an oil absorption in the range of
from about 19 to about 23%.
37. The dry-milled ATH particles according to claim 35 wherein the
dry-milled ATH particles have: a) a BET in the range of from about
3 to about 6 m.sup.2/g, a d.sub.50 in the range of from about 1.5
to about 2.5 .mu.m, an oil absorption in the range of from about 23
to about 30%, an r.sub.50 in the range of from about 0.2 to about
0.33 .mu.m, a V.sub.max in the range of from about 390 to about 480
mm.sup.3/g, a total soda content of less than about 0.2 wt. %, an
electrical conductivity in the range of less than about 100
.mu.S/cm, a soluble soda content in the range of from 0.001 to less
than 0.02 wt %, based on the dry-milled ATH particles, a
non-soluble soda content in the range of from about 70 to about
99.8% of the total soda content of the dry-milled ATH and a thermal
stability, determined by thermogravimetric analysis, as described
in Table 1: TABLE-US-00004 TABLE 1 1 wt. % TGA (.degree. C.) 2 wt.
% TGA (.degree. C.) 210-225 220-235
or b) a BET in the range of from about 6 to about 9 m.sup.2/g, a
d.sub.50 in the range of from about 1.3 to about 2.0 .mu.m, an oil
absorption in the range of from about 25 to about 40%, an r.sub.50
in the range of from about 0.185 to about 0.325 .mu.m, a V.sub.max
in the range of from about 400 to about 600 mm.sup.3/g, a total
soda content of less than about 0.3 wt. %, an electrical
conductivity in the range of less than about 150 .mu.S/cm, a
soluble soda content in the range of from 0.001 to less than 0.03
wt %, based on the dry-milled ATH particles, a non-soluble soda
content in the range of from about 70 to about 99.8% of the total
soda content of the dry-milled ATH and a thermal stability,
determined by thermogravimetric analysis, as described in Table 2:
TABLE-US-00005 TABLE 2 1 wt. % TGA (.degree. C.) 2 wt. % TGA
(.degree. C.) 200-215 210-225
or c) a BET in the range of from about 9 to about 15 m.sup.2/g and
a d.sub.50 in the range of from about 0.9 to about 1.8 .mu.m, an
oil absorption in the range of from about 25 to about 50%, an
r.sub.50 in the range of from about 0.09 to about 0.21 .mu.m, a
V.sub.max in the range of from about 300 to about 700 mm.sup.3/g, a
total soda content of less than about 0.4 wt. %, an electrical
conductivity in the range of less than about 200 .mu.S/cm, a
soluble soda content in the range of from 0.001 to less than 0.04
wt %, based on the dry-milled ATH particles, a non-soluble soda
content in the range of from about 70 to about 99.8% of the total
soda content of the dry-milled ATH and a thermal stability,
determined by thermogravimetric analysis, as described in Table 3:
TABLE-US-00006 TABLE 3 1 WT. % TGA (.degree. C.) 2 WT. % TGA
(.degree. C.) 195-210 205-220
38. The dry-milled particles according to claim 35 wherein said
dry-milled ATH particles have a non-soluble soda content in the
range of from about 70 to about 99 wt. % of the total soda content
of the dry-milled ATH.
39. A flame retarded polymer formulation comprising at least one
synthetic resin and in the range of from about 5 wt % to about 90
wt %, based on the weight of the flame retarded polymer formulation
of the dry-milled ATH particles according to claim 35.
40. The flame retarded polymer formulation according to claim 39
wherein said dry-milled ATH particles having a V.sub.max in the
range of from about 300 to about 700 mm.sup.3/g and/or an r.sub.50
in the range of from about 0.09 to about 0.33 .mu.m, and one or
more of the following characteristics: i) a d.sub.50 of from about
0.5 to about 2.5 .mu.m; ii) a total soda content of less than about
0.4 wt. %, based on the total weight of the dry-milled ATH
particles; iii) an oil absorption of less than about 50%, as
determined by ISO 787-5:1980; and iv) a specific surface area (BET)
as determined by DIN-66132 of from about 1 to about 15 m.sup.2/g,
wherein the electrical conductivity of the dry-milled ATH particles
is less than about 200 .mu.S/cm, measured in water at 10 wt. % of
the ATH in water.
41. The flame retarded polymer formulation according to claim 40
wherein said dry-milled ATH particles have an oil absorption in the
range of from about 19 to about 23%.
42. The flame retarded polymer formulation according to claim 40
wherein the dry-milled ATH particles have: a) a BET in the range of
from about 3 to about 6 m.sup.2/g, a d.sub.50 in the range of from
about 1.5 to about 2.5 .mu.m, an oil absorption in the range of
from about 23 to about 30%, an r.sub.50 in the range of from about
0.2 to about 0.33 .mu.m, a V.sub.max in the range of from about 390
to about 480 mm.sup.3/g, a total soda content of less than about
0.2 wt. %, an electrical conductivity in the range of less than
about 100 .mu.S/.mu.m, a soluble soda content in the range of from
0.001 to less than 0.02 wt %, based on the dry-milled ATH
particles, a non-soluble soda content in the range of from about 70
to about 99.8% of the total soda content of the dry-milled ATH and
a thermal stability, determined by thermogravimetric analysis, as
described in Table 1: TABLE-US-00007 TABLE 1 1 wt. % TGA (.degree.
C.) 2 wt. % TGA (.degree. C.) 210-225 220-235
or b) a BET in the range of from about 6 to about 9 m.sup.2/g, a
d.sub.50 in the range of from about 1.3 to about 2.0 .mu.m, an oil
absorption in the range of from about 25 to about 40%, an r.sub.50
in the range of from about 0.185 to about 0.325 .mu.m, a V.sub.max
in the range of from about 400 to about 600 mm.sup.3/g, a total
soda content of less than about 0.3 wt. %, an electrical
conductivity in the range of less than about 150 .mu.S/cm, a
soluble soda content in the range of from 0.001 to less than 0.03
wt %, based on the dry-milled ATH particles, a non-soluble soda
content in the range of from about 70 to about 99.8% of the total
soda content of the dry-milled ATH and a thermal stability,
determined by thermogravimetric analysis, as described in Table 2:
TABLE-US-00008 TABLE 2 1 wt. % TGA (.degree. C.) 2 wt. % TGA
(.degree. C.) 200-215 210-225
or c) a BET in the range of from about 9 to about 15 m.sup.2/g and
a d.sub.50 in the range of from about 0.9 to about 1.8 .mu.m, an
oil absorption in the range of from about 25 to about 50%, an
r.sub.50 in the range of from about 0.09 to about 0.21 .mu.m, a
V.sub.max in the range of from about 300 to about 700 mm.sup.3/g, a
total soda content of less than about 0.4 wt. %, an electrical
conductivity in the range of less than about 200 .mu.S/cm, a
soluble soda content in the range of from 0.001 to less than 0.04
wt %, based on the dry-milled ATH particles, a non-soluble soda
content in the range of from about 70 to about 99.8% of the total
soda content of the dry-milled ATH and a thermal stability,
determined by thermogravimetric analysis, as described in Table 3:
TABLE-US-00009 TABLE 3 1 WT. % TGA (.degree. C.) 2 WT. % TGA
(.degree. C.) 195-210 205-220
43. The flame retarded polymer formulation according to claim 42
wherein said dry-milled ATH particles have a non-soluble soda
content in the range of from about 70 to about 99 wt. % of the
total soda content of the dry-milled ATH.
44. A molded or extruded article made from the flame retarded
polymer formulation according to any of claims 39-43.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the production of mineral
flame retardants. More particularly the present invention relates
to a novel process for the production of aluminum hydroxide flame
retardants having improved thermal stability.
BACKGROUND OF THE INVENTION
[0002] Aluminum hydroxide has a variety of alternative names such
as aluminum hydrate, aluminum trihydrate etc., but is commonly
referred to as ATH. ATH particles, finds many uses as a filler in
many materials such as, for example, papers, resins, rubber,
plastics etc. These products find use in diverse commercial
applications such as cable and wire sheaths, conveyor belts,
thermoplastics moldings, adhesives, etc. ATH is typically used to
improve the flame retardancy of such materials and also acts as a
smoke suppressant. ATH also commonly finds use as a flame retardant
in resins used to fabricate printed wiring circuit boards. Thus,
the thermal stability of the ATH is a quality closely monitored by
end users. For example, in printed circuit board applications, the
thermal stability of the laminates used in constructing the boards
must be sufficiently high to allow lead free soldering.
[0003] Methods for the synthesis and production of ATH are well
known in the art. However, the demand for tailor made ATH grades is
increasing, and the current processes are not capable of producing
all of these grades. Thus, as the demand for tailor made ATH grades
increases, the demand for processes to produce these grades is also
increasing.
SUMMARY OF THE INVENTION
[0004] While empirical evidence indicates that the thermal
stability of an ATH is linked to the total soda content of the ATH,
the inventors hereof have discovered and believe, while not wishing
to be bound by theory, that the improved thermal stability of the
ATH of the present invention is linked to the non-soluble soda
content, which is typically in the range of from about 70 to about
99 wt. %, based on the weight of the total soda, of the total soda
content, with the remainder being soluble soda.
[0005] The inventors hereof also believe, while not wishing to be
bound by theory, that the wettability of ATH particles with resins
depends on the morphology of the ATH particles, and the inventors
hereof have unexpectedly discovered that by using the process of
the present invention, ATH particles having an improved wettability
in relation to ATH particles currently available can be produced.
While not wishing to be bound by theory, the inventors hereof
believe that this improved wettability is attributable to an
improvement in the morphology of the ATH particles produced by the
process disclosed herein.
[0006] The inventors hereof further believe, while not wishing to
be bound by theory, that this improved morphology is attributable
to the total specific pore volume and/or the median pore radius of
the ATH product particles. The inventors hereof believe that, for a
given polymer molecule, an ATH product having a higher structured
aggregate contains more and bigger pores and seems to be more
difficult to wet, leading to difficulties (higher variations of the
power draw on the motor) during compounding in kneaders like Buss
Ko-kneaders or twin-screw extruders or other machines known in the
art and used to this purpose. Therefore, the inventors hereof have
discovered that an ATH filler characterized by smaller median pore
sizes and/or lower total pore volumes correlates with an improved
wetting with polymeric materials and thus results in improved
compounding behavior, i.e. less variations of the power draw of the
engines (motors) of compounding machines used to compound a flame
retarded resin containing the ATH filler. The inventors hereof have
discovered that the process of the present invention is especially
well-suited for producing an ATH having these characteristics.
[0007] Thus, in one embodiment, the present invention produces
dry-milled ATH particles having a V.sub.max, i.e. maximum specific
pore volume at about 1000 bar, in the range of from about 300 to
about 700 mm.sup.3/g and/or an r.sub.50, i.e. a pore radius at 50%
of the relative specific pore volume, in the range of from about
0.09 to about 0.33 .mu.m, and one or more, preferably two or more,
and more preferably three or more, in some embodiments all, of the
following characteristics: i) a d.sub.50 of from about 0.5 to about
2.5 .mu.m; ii) a total soda content of less than about 0.4 wt. %,
based on the total weight of the dry-milled ATH particles; iii) an
oil absorption of less than about 50%, as determined by ISO
787-5:1980; and iv) a specific surface area (BET) as determined by
DIN-66132 of from about 1 to about 15 m.sup.2/g, wherein the
electrical conductivity of the dry-milled ATH particles is less
than about 200 .mu.S/cm, measured in water at 10 wt. % of the ATH
in water.
[0008] In another embodiment, the present invention relates to a
flame retarded resin formulation comprising the dry-milled ATH
particles produced by the process of the present invention.
[0009] In some embodiments, the dry-milled ATH particles of the
present invention are further characterized as having a soluble
soda content of less than about 0.1 wt. %.
[0010] The present invention also relates to a process for
producing dry-milled ATH. The process generally comprises spray
drying an aluminum hydroxide slurry or filter cake to produce
spray-dried aluminum hydroxide particles, and dry-milling said
spray-dried aluminum hydroxide particles thus producing dry-milled
ATH particles as described herein.
DETAILED DESCRIPTION OF THE INVENTION
[0011] It should be noted that all particle diameter measurements,
i.e. d.sub.50 values, disclosed herein were measured by laser
diffraction using a Cilas 1064 L laser spectrometer from
Quantachrome. Generally, the procedure used herein to measure the
d.sub.50, can be practiced by first introducing a suitable
water-dispersant solution (preparation see below) into the
sample-preparation vessel of the apparatus. The standard
measurement called "Particle Expert" is then selected, the
measurement model "Range 1" is also selected, and
apparatus-internal parameters, which apply to the expected particle
size distribution, are then chosen. It should be noted that during
the measurements the sample is typically exposed to ultrasound for
about 60 seconds during the dispersion and during the measurement.
After a background measurement has taken place, from about 75 to
about 100 mg of the sample to be analyzed is placed in the sample
vessel with the water/dispersant solution and the measurement
started. The water/dispersant solution can be prepared by first
preparing a concentrate from 500 g Calgon, available from KMF
Laborchemie, with 3 liters of CAL Polysalt, available from BASF.
This solution is made up to 10 liters with deionized water. 100 ml
of this original 10 liters is taken and in turn diluted further to
10 liters with deionized water, and this final solution is used as
the water-dispersant solution described above.
Slurry and Filter Cake
[0012] In one embodiment of the present invention a slurry or a
filter cake containing ATH particles is spray dried to produce
spray dried ATH particles which are then dry milled, thus producing
dry milled ATH particles. In one preferred embodiment, a slurry is
spray-dried and in another preferred embodiment, a filter cake is
spray-dried.
[0013] The slurry or the filter cake typically contains in the
range of from about 1 to about 85 wt. % ATH particles, based on the
total weight of the slurry or the filter cake. In some embodiments,
the slurry or the filter cake contains in the range of from about
25 to about 85 wt. % ATH particles, in other embodiments in the
range of from about 40 to about 70 wt. % ATH particles, sometimes
in the range of from about 55 to about 65 wt. % ATH particles, all
on the same basis. In other embodiments, the slurry or the filter
cake contains in the range of from about 40 to about 60 wt. % ATH
particles, sometimes in the range of from about 45 to about 55 wt.
% ATH particles, both on the same basis. In still other
embodiments, the slurry or the filter cake contains in the range of
from about 25 to about 50 wt. % ATH particles, sometimes in the
range of from about 30 to about 45 wt. % ATH particles, both on the
same basis.
[0014] The slurry or the filter cake used in the practice of the
present invention can be obtained from any process used to produce
ATH particles. In some embodiments, the slurry or the filter cake
is obtained from a process that involves producing ATH particles
through precipitation and filtration. In an exemplary embodiment,
the slurry or the filter cake is obtained from a process that
comprises dissolving crude aluminum hydroxide in caustic soda to
form a sodium aluminate liquor, which is cooled and filtered thus
forming a sodium aluminate liquor useful in this exemplary
embodiment. The sodium aluminate liquor thus produced typically has
a molar ratio of Na.sub.2O to Al.sub.2O.sub.3 in the range of from
about 1.4:1 to about 1.55:1. In order to precipitate ATH particles
from the sodium aluminate liquor, ATH seed particles are added to
the sodium aluminate liquor in an amount in the range of from about
1 g of ATH seed particles per liter of sodium aluminate liquor to
about 3 g of ATH seed particles per liter of sodium aluminate
liquor thus forming a process mixture. The ATH seed particles are
added to the sodium aluminate liquor when the sodium aluminate
liquor is at a liquor temperature of from about 45 to about
80.degree. C. After the addition of the ATH seed particles, the
process mixture is stirred for about 100 h or alternatively until
the molar ratio of Na.sub.2O to Al.sub.2O.sub.3 is in the range of
from about 2.2:1 to about 3.5:1, thus forming an ATH suspension.
The obtained ATH suspension typically comprises from about 80 to
about 160 g/l ATH, based on the suspension. However, the ATH
concentration can be varied to fall within the ranges described
above. The obtained ATH suspension is then filtered and washed to
remove impurities therefrom, thus forming a filter cake. The filter
cake can be washed one, or in some embodiments more than one, times
with water, preferably de-salted water. This filter cake can then
be directly spray dried.
[0015] However, in some embodiments, the filter cake can be
re-slurried with water to form a slurry, or in a preferred
embodiment, at least one, preferably only one, dispersing agent is
added to the filter cake to form a slurry having an ATH
concentration in the above-described ranges. It should be noted
that it is also within the scope of the present invention to
re-slurry the filter cake with a combination of water and a
dispersing agent. Non-limiting examples of dispersing agents
suitable for use herein include polyacrylates, organic acids,
naphtalensulfonate/formaldehyde condensate,
fatty-alcohol-polyglycol-ether, polypropylene-ethylenoxid,
polyglycol-ester, polyamine- ethylenoxid, phosphate,
polyvinylalcohole. If the slurry comprises a dispersing agent, the
slurry may contain up to about 80 wt. % ATH, based on the total
weight of the slurry, because of the effects of the dispersing
agent. In this embodiment, the remainder of the slurry or the
filter cake (i.e. not including the ATH particles and the
dispersing agent(s)) is typically water, although some reagents,
contaminants, etc. may be present from precipitation.
[0016] The inventors hereof, while not wishing to be bound by
theory, believe that the improved morphology of the ATH particles
produced by the present invention is at least partially
attributable to the process used to precipitate the ATH. Thus,
while dry milling techniques are known in the art, the inventors
hereof have discovered that by using the precipitation and
filtration processes described herein, including preferred
embodiments, along with the dry milling process described herein,
ATH particles having improved morphology, as described below, can
be readily produced.
ATH Particles in the Slurry and/or Filter Cake
[0017] In some embodiments, the BET of the ATH particles in the
filter cake and/or slurry is in the range of from about 1.0 to
about 4.0 m.sup.2/g. In these embodiments, it is preferred that the
ATH particles in the filter cake and/or slurry have a BET in the
range of from about 1.5 to about 2.5 m.sup.2/g. In these
embodiments, the ATH particles in the filter cake and/or slurry can
also be, and preferably are, characterized by a d.sub.50 in the
range of from about 1.8 to about 3.5 .mu.m, preferably in the range
of from about 1.8 to about 2.5 .mu.m, which is coarser than the
dry-milled ATH particles produced herein.
[0018] In other embodiments, the BET of the ATH particles in the
filter cake and/or slurry is in the range of from about 4.0 to
about 8.0 m.sup.2/g, preferably in the range of from about 5 to
about 7 m.sup.2/g. In these embodiments, the ATH particles in the
filter cake and/or slurry can also be, and preferably are,
characterized by a d.sub.50 in the range of from about 1.5 to about
2.5 .mu.m, preferably in the range of from about 1.6 to about 2.0
.mu.m, which is coarser than the dry-milled ATH particles produced
herein.
[0019] In still other embodiments, the BET of the ATH particles in
the filter cake and/or slurry is in the range of from about 8.0 to
about 14 m.sup.2/g, preferably in the range of from about 9 to
about 12 m.sup.2/g. In these embodiments, the ATH particles in the
filter cake and/or slurry can also be, and preferably are,
characterized by a d.sub.50 in the range of from about 1.5 to about
2.0 .mu.m, preferably in the range of from about 1.5 to about 1.8
.mu.m, which is coarser than the dry-milled ATH particles produced
herein.
[0020] By coarser than the mill-dried ATH particles, it is meant
that the upper limit of the d.sub.50 value of the ATH particles in
the filter cake and/or slurry is generally at least about 0.2 .mu.m
higher than the upper limit of the d.sub.50 of the dry-milled ATH
particles produced herein.
[0021] The ATH particles in the slurry and/or filter cake used in
the present invention can also be characterized, and preferably are
characterized by, a total soda content of less than about 0.2 wt.
%, based on the ATH particles in the slurry or filter cake. In
preferred embodiments, if the soluble soda content is a
characteristic of the ATH particles, the total soda content is less
than 0.18 wt. %, more preferably less than 0.12 wt. %, based on the
total weight of the ATH particles in the slurry and/or filter cake.
The total soda content of the ATH can be measured by using a flame
photometer M7DC from Dr. Bruno Lange GmbH, Dusseldorf/Germany. In
the present invention, the total soda content of the ATH particles
was measured by first adding 1 g of ATH particles into a quartz
glass bowl, then adding 3 ml of concentrated sulfuric acid to the
quartz glass bowl, and carefully agitating the contents of the
glass bowl with a glass rod. The mixture is then observed, and if
the ATH-crystals do not completely dissolve, another 3 ml of
concentrated sulfuric acid is added and the contents mixed again.
The bowl is then heated on a heating plate until the excess
sulfuric acid is completely evaporated. The contents of the quartz
glass bowl are then cooled to about room temperature, and about 50
ml of deionized water is added to dissolve any salts in the bowl.
The contents of the bowl are then maintained at increased
temperature for about 20 minutes until the salts are dissolved. The
contents of the glass bowl are then cooled to about 20.degree. C.,
transferred into a 500 ml measuring flask, which is then filled up
with deionized water and homogenized by shaking. The solution in
the 500 ml measuring flask is then analyzed with the flame
photometer for total soda content of the ATH particles.
[0022] The ATH particles in the slurry and/or filter cake used in
the present invention can also be characterized, and preferably are
characterized by, a soluble soda content of less than about 0.1 wt.
%, based on the ATH particles in the slurry and/or filter cake. In
other embodiments, the ATH particles in the filter cake and/or
slurry can be further characterized as having a soluble soda
content in the range of from greater than about 0.001 to about 0.1
wt. %, in some embodiments in the range of from about 0.02 to about
0.1 wt. %, both based on the ATH particles in the filter cake
and/or slurry. While in other embodiments, the ATH particles in the
filter cake and/or slurry can be further characterized as having a
soluble soda content in the range of from about 0.001 to less than
0.04 wt %, in some embodiments in the range of from about 0.001 to
less than 0.03 wt %, in other embodiments in the range of from
about 0.001 to less than 0.02 wt %, on the same basis. The soluble
soda content is measured via flame photometry. To measure the
soluble soda content, a solution of the sample was prepared as
follows: 20 g of the sample are transferred into a 1000 ml
measuring flask and leached out with about 250 ml of deionized
water for about 45 minutes on a water bath at approx. 95.degree. C.
The flask is then cooled to 20.degree. C., filled to the
calibration mark with deionized water, and homogenized by shaking.
After settling of the sample, a clear solution forms in the flask
neck, and, with the help of a filtration syringe or by using a
centrifuge, as much of the solution as needed for the measurement
in the flame photometer can be removed from the flask.
[0023] The ATH particles in the slurry and/or filter cake used in
the practice of the present invention can also be described as
having a non-soluble soda content, as described herein, in the
range of from about 70 to about 99.8% of the total soda content,
with the remainder being soluble soda. While empirical evidence
indicates that the thermal stability is linked to the total soda
content of the ATH, the inventors hereof, while not wishing to be
bound by theory, believe that the improved thermal stability of the
dry-milled ATH particles produced by the process of the present
invention is linked to the non-soluble soda content, which is
typically in the range of from about 70 to about 99.8 wt. % of the
total soda content, with the remainder being soluble soda. In some
embodiments of the present invention, the total soda content of the
ATH particles in the slurry and/or filter cake used in the practice
of the present invention is typically in the range of less than
about 0.20 wt. %, based on the ATH particles in the slurry and/or
filter cake, preferably in the range of less than about 0.18 wt. %,
based on the ATH particles in the slurry and/or filter cake, more
preferably in the range of less than about 0.12 wt. %, on the same
basis. In other embodiments of the present invention, the total
soda content of the ATH particles in the slurry and/or filter cake
used in the practice of the present invention is typically in the
range of less than about 0.30 wt. %, based on the ATH particles in
the slurry and/or filter cake, preferably in the range of less than
about 0.25 wt. %, based on the ATH particles in the slurry and/or
filter cake, more preferably in the range of less than about 0.20
wt. %, on the same basis. In still other embodiments of the present
invention, the total soda content of the ATH particles in the
slurry and/or filter cake used in the practice of the present
invention is typically in the range of less than about 0.40 wt. %,
based on the ATH particles in the slurry and/or filter cake,
preferably in the range of less than about 0.30 wt. %, based on the
ATH particles in the slurry and/or filter cake, more preferably in
the range of less than about 0.25 wt. %, on the same basis.
Spray-Drying
[0024] Spray drying is a technique that is commonly used in the
production of aluminum hydroxide. This technique generally involves
the atomization of an ATH feed, here the milled ATH slurry or the
filter cake, through the use of nozzles and/or rotary atomizers.
The atomized feed is then contacted with a hot gas, typically air,
and the spray dried ATH is then recovered from the hot gas stream.
The contacting of the atomized feed can be conducted in either a
counter or co-current fashion, and the gas temperature,
atomization, contacting, and flow rates of the gas and/or atomized
feed can be controlled to produce ATH particles having desired
product properties.
[0025] The recovery of the spray dried ATH can be achieved through
the use of recovery techniques such as filtration or just allowing
the spray-dried particles to fall to collect in the spray drier
where they can be removed, but any suitable recovery technique can
be used. In preferred embodiments, the spray dried ATH is recovered
from the spray drier by allowing it to settle, and screw conveyors
recover it from the spray-drier and subsequently convey through
pipes into a silo by means of compressed air.
[0026] The spray-drying conditions are conventional and are readily
selected by one having ordinary skill in the art with knowledge of
the desired ATH particle product qualities, described below
Generally, these conditions include inlet air temperatures between
typically 250 and 550.degree. C. and outlet air temperatures
typically between 105 and 150.degree. C.
[0027] The spray-dried ATH is then subjected to dry-milling.
Dry-Milling
[0028] By dry-milling, it is meant that the spray-dried ATH is
subjected to a further treatment wherein the ATH is de-agglomerated
with little reduction in the particle size of the spray-dried ATH.
By "little particle size reduction" it is meant that the d.sub.50
of the dry-milled ATH is in the range of from about 40% to about
90% of the ATH in the slurry or the filter cake prior to spray
drying. In preferred embodiments, the d.sub.50 of the dry-milled
ATH is in the range of from about 60% to about 80% of the ATH in
the slurry or the filter cake prior to spray drying, more
preferably within the range of from about 70% to about 75% of the
ATH in the slurry or the filter cake prior to spray drying.
[0029] The mill used in dry-milling the spray dried ATH can be
selected from any dry-mills known in the art. Non-limiting examples
of suitable dry mills include ball or media mills, cone and
gyratory crushers, disk attrition mills, colloid and roll mills,
screen mills and granulators, hammer and cage mills, pin and
universal mills, impact mills and breakers, jaw crushers, jet and
fluid energy mills, roll crushers, disc mills, and vertical rollers
and dry pans, vibratory mills.
[0030] The dry-milled ATH recovered from the dry-milling of the
spray-dried ATH can be classified via any classification techniques
known because during dry milling, agglomerates can be produced,
depending on the mill used. Non-limiting examples of suitable
classification techniques include air classification. It should be
noted that some mills have a built-in air classifier; if this is
not the case, a separate air classifier can be used. If a pin mill
is not used in the dry-milling, the dry-milled ATH can be subjected
to further treatment in one or more pin mills.
[0031] The dry-milling of the spray-dried ATH is conducted under
conditions effective at producing a dry-milled ATH particles having
the properties discussed herein.
Dry-Milled ATH Particles According to the Present Invention
[0032] In general, the dry-milling of the spray-dried ATH particles
produces dry-milled ATH particles that are generally characterized
as having a specific total specific pore volume and/or median pore
radius ("r.sub.50") in addition to one or more, preferably two or
more, and more preferably three or more, in some embodiments all,
of the following characteristics: i) a d.sub.50 of from about 0.5
to about 2.5 .mu.m; ii) a total soda content of less than about 0.4
wt. %, based on the total weight of the dry-milled ATH particles;
iii) an oil absorption of less than about 50%, as determined by ISO
787-5:1980; and iv) a specific surface area (BET) as determined by
DIN-66132 of from about 1 to about 15 m.sup.2/g, wherein the
electrical conductivity of the dry-milled ATH particles is less
than about 200 .mu.S/cm, measured in water at 10 wt. % of the ATH
in water.
[0033] As stated above, the inventors hereof believe that, for a
given polymer molecule, ATH particles having a higher structured
aggregate contain more and bigger pores and seems to be more
difficult to wet, leading to difficulties (higher variations of the
power draw on the motor) during compounding in kneaders like Buss
Ko-kneaders or twin-screw extruders or other machines known in the
art and used to this purpose. The inventors hereof have discovered
that the dry-milled ATH particles of the present invention are
characterized by smaller median pore sizes and/or lower total pore
volumes, which correlates with an improved wetting with polymeric
materials and thus results in improved compounding behavior, i.e.
less variations of the power draw of the engines (motors) of
compounding machines used to compound a flame retarded resin
containing the ATH filler.
[0034] The r.sub.50 and the specific pore volume at about 1000 bar
("V.sub.max") of the spray-dried ATH particles can be derived from
mercury porosimetry. The theory of mercury porosimetry is based on
the physical principle that a non-reactive, non-wetting liquid will
not penetrate pores until sufficient pressure is applied to force
its entrance. Thus, the higher the pressure necessary for the
liquid to enter the pores, the smaller the pore size. A smaller
pore size and/or a lower total specific pore volume were found to
correlate to better wettability of the dry-milled ATH particles.
The pore size of the dry-milled ATH particles can be calculated
from data derived from mercury porosimetry using a Porosimeter 2000
from Carlo Erba Strumentazione, Italy. According to the manual of
the Porosimeter 2000, the following equation is used to calculate
the pore radius r from the measured pressure p: r=-2 .gamma.
cos(.theta.)/p; wherein .theta. is the wetting angle and .gamma. is
the surface tension. The measurements taken herein used a value of
141.3.degree. for .theta. and .gamma. was set to 480 dyn/cm.
[0035] In order to improve the repeatability of the measurements,
the pore size of the dry-milled ATH particles was calculated from
the second ATH intrusion test run, as described in the manual of
the Porosimeter 2000. The second test run was used because the
inventors observed that an amount of mercury having the volume
V.sub.0 remains in the sample of the dry-milled ATH particles after
extrusion, i.e. after release of the pressure to ambient pressure.
Thus, the r.sub.50 can be derived from this data as explained
below.
[0036] In the first test run, a sample of dry-milled ATH particles
was prepared as described in the manual of the Porosimeter 2000,
and the pore volume was measured as a function of the applied
intrusion pressure p using a maximum pressure of 1000 bar. The
pressure was released and allowed to reach ambient pressure upon
completion of the first test run. A second intrusion test run
(according to the manual of the Porosimeter 2000) utilizing the
same dry-milled ATH sample, unadulterated, from the first test run
was performed, where the measurement of the specific pore volume
V(p) of the second test run takes the volume V.sub.0 as a new
starting volume, which is then set to zero for the second test
run.
[0037] In the second intrusion test run, the measurement of the
specific pore volume V(p) of the sample was again performed as a
function of the applied intrusion pressure using a maximum pressure
of 1000 bar. The pore volume at about 1000 bar, i.e. the maximum
pressure used in the measurement, is referred to as V.sub.max
herein.
[0038] From the second dry-milled ATH intrusion test run, the pore
radius r was calculated by the Porosimeter 2000 according to the
formula r=-2 .gamma. cos(.theta.)/p; wherein .theta. is the wetting
angle, .gamma. is the surface tension and p the intrusion pressure.
For all r-measurements taken herein, a value of 141.3.degree. for
.theta. was used and .gamma. was set to 480 dyn/cm. If desired, the
specific pore volume can be plotted against the pore radius r for a
graphical depiction of the results generated. The pore radius at
50% of the relative specific pore volume, by definition, is called
median pore radius r.sub.50 herein.
[0039] For a graphical representation of r.sub.50 and V.sub.max,
please see U.S. Provisional Patent Applications 60/818,632;
60/818,633; 60/818,670; 60/815,515; and 60/818,426, which are all
incorporated herein in their entirety.
[0040] The procedure described above was repeated using samples of
dry-milled ATH particles according to the present invention, and
the dry-milled ATH particles were found to have an r.sub.50, i.e. a
pore radius at 50% of the relative specific pore volume, in the
range of from about 0.09 to about 0.33 .mu.m. In some embodiments
of the present invention, the r.sub.50 of the dry-milled ATH
particles is in the range of from about 0.20 to about 0.33 .mu.m,
preferably in the range of from about 0.2 to about 0.3 .mu.m. In
other embodiments, the r.sub.50 is in the range of from about 0.185
to about 0.325 .mu.m, preferably in the range of from about 0.185
to about 0.25 .mu.m. In still other preferred embodiments, the
r.sub.50 is in the range of from about 0.09 to about 0.21 .mu.m,
more preferably in the range of from about 0.09 to about 0.165
.mu.m.
[0041] The dry-milled ATH particles can also be characterized as
having a V.sub.max, i.e. maximum specific pore volume at about 1000
bar, in the range of from about 300 to about 700 mm.sup.3/g. In
some embodiments of the present invention, the V.sub.max of the
dry-milled ATH particles is in the range of from about 390 to about
480 mm.sup.3/g, preferably in the range of from about 410 to about
450 mm.sup.3/g. In other embodiments, the V.sub.max is in the range
of from about 400 to about 600 mm.sup.3/g, preferably in the range
of from about 450 to about 550 mm.sup.3/g. In yet other
embodiments, the V.sub.max is in the range of from about 300 to
about 700 mm.sup.3/g, preferably in the range of from about 350 to
about 550 mm.sup.3/g.
[0042] The dry-milled ATH particles can also be characterized as
having an oil absorption, as determined by ISO 787-5:1980, of less
than bout 50%, sometimes in the range of from about 1 to about 50%.
In some embodiments, the dry-milled ATH particles are characterized
as having an oil absorption in the range of from about 23 to about
30%, preferably in the range of from about 24% to about 29%, more
preferably in the range of from about 25% to about 28%. In other
embodiments, the dry-milled ATH particles are characterized as
having an oil absorption in the range of from about 25% to about
40%, preferably in the range of from about 25% to about 35%, more
preferably in the range of from about 26% to about 30%. In still
other embodiments, the dry-milled ATH particles are characterized
as having an oil absorption in the range of from about 25 to about
50%, preferably in the range of from about 26% to about 40%, more
preferably in the range of from about 27% to about 32%. In other
embodiments, the oil absorption of the dry-milled ATH particles is
in the range of from about 19% to about 23%, and in still other
embodiments, the oil absorption of the dry-milled ATH particles
produced is in the range of from about 21% to about 25%.
[0043] The dry-milled ATH particles can also be characterized as
having a BET specific surface area, as determined by DIN-66132, in
the range of from about 1 to 15 m.sup.2/g. In some embodiments, the
dry-milled ATH particles have a BET specific surface in the range
of from about 3 to about 6 m.sup.2/g, preferably in the range of
from about 3.5 to about 5.5 m.sup.2/g. In other embodiments, the
dry-milled ATH particles have a BET specific surface of in the
range of from about 6 to about 9 m.sup.2/g, preferably in the range
of from about 6.5 to about 8.5 m.sup.2/g. In still other
embodiments, the dry-milled ATH particles have a BET specific
surface in the range of from about 9 to about 15 m.sup.2/g,
preferably in the range of from about 10.5 to about 12.5
m.sup.2/g,
[0044] The dry-milled ATH particles can also be characterized as
having a d.sub.50 in the range of from about 0.5 to 2.5 .mu.m. In
some embodiments, the dry-milled ATH particles produced by the
present invention have a d.sub.50 in the range of from about 1.5 to
about 2.5 .mu.m, preferably in the range of from about 1.8 to about
2.2 .mu.m. In other embodiments, the dry-milled ATH particles have
a d.sub.50 in the range of from about 1.3 to about 2.0 .mu.m,
preferably in the range of from about 1.4 to about 1.8 .mu.m. In
still other embodiments, the dry-milled ATH particles have a
d.sub.50 in the range of from about 0.9 to about 1.8 .mu.m, more
preferably in the range of from about 1.1 to about 1.5 .mu.m.
[0045] The dry-milled ATH particles can also be characterized as
having a total soda content of less than about 0.4 wt. %, based on
the dry-milled ATH particles. In some embodiments, if the soluble
soda content is a characteristic of the dry-milled ATH particles,
the total soda content is less than about 0.20 wt. %, preferably
less than about 0.18 wt. %, more preferably less than 0.12 wt. %,
all based on the total weight of the dry-milled ATH particles. In
other embodiments, if the soluble soda content is a characteristic
of the dry-milled ATH particles, the total soda content is less
than about 0.30, preferably less than about 0.25 wt. %, more
preferably less than 0.20 wt. %, based on the total weight of the
dry-milled ATH particles. In other embodiments, if the soluble soda
content is a characteristic of the dry-milled ATH particles, the
total soda content is less than about 0.40, preferably less than
about 0.30 wt. %, more preferably less than 0.25 wt. %, based on
the total weight of the dry-milled ATH particles. The total soda
content can be measured according to the procedure outlined
above.
[0046] The dry-milled ATH particles can also be characterized as
having a thermal stability, as described in Tables 1, 2, and 3,
below.
TABLE-US-00001 TABLE 1 1 wt. % TGA (.degree. C.) 2 wt. % TGA
(.degree. C.) Typical 210-225 220-235 Preferred 210-220 220-230
More Preferred 214-218 224-228
TABLE-US-00002 TABLE 2 1 wt. % TGA (.degree. C.) 2 wt. % TGA
(.degree. C.) Typical 200-215 210-225 Preferred 200-210 210-220
More Preferred 200-205 210-215
TABLE-US-00003 TABLE 3 1 wt. % TGA (.degree. C.) 2 wt. % TGA
(.degree. C.) Typical 195-210 205-220 Preferred 195-205 205-215
More Preferred 195-200 205-210
[0047] Thermal stability, as used herein, refers to release of
water of the dry-milled ATH particles and can be assessed directly
by several thermoanalytical methods such as thermogravimetric
analysis ("TGA"), and in the present invention, the thermal
stability of the dry-milled ATH particles was measured via TGA.
Prior to the measurement, the dry-milled ATH particle samples were
dried in an oven for 4 hours at about 105.degree. C. to remove
surface moisture. The TGA measurement was then performed with a
Mettler Toledo by using a 70 .mu.l alumina crucible (initial weight
of about 12 mg) under N.sub.2 (70 ml per minute) with the following
heating rate: 30.degree. C. to 150.degree. C. at 10.degree. C. per
min, 150.degree. C. to 350.degree. C. at 1.degree. C. per min,
350.degree. C. to 600.degree. C. at 10.degree. C. per min. The TGA
temperature of the dry-milled ATH particles (pre-dried as described
above) was measured at 1 wt. % loss and 2 wt. % loss, both based on
the weight of the dry-milled ATH particles. It should be noted that
the TGA measurements described above were taken using a lid to
cover the crucible.
[0048] The dry-milled ATH particles can also be characterized as
having an electrical conductivity in the range of less than about
200 .mu.S/cm, in some embodiments less than 150 .mu.S/cm, and in
other embodiments, less than 100 .mu.S/cm. In other embodiments,
the electrical conductivity of the dry-milled ATH particles is in
the range of about 10 to about 45 .mu.S/cm. It should be noted that
all electrical conductivity measurements were conducted on a
solution comprising water and about at 10 wt. % dry-milled ATH,
based on the solution, as described below.
[0049] The electrical conductivity was measured by the following
procedure using a MultiLab 540 conductivity measuring instrument
from Wissenschaftlich-Technische-Werkstatten GmbH,
Weilheim/Germany: 10 g of the sample to be analyzed and 90 ml
deionized water (of ambient temperature) are shaken in a 100 ml
Erlenmeyer flask on a GFL 3015 shaking device available from
Gesellschaft for Labortechnik mbH, Burgwedel/Germany for 10 minutes
at maximum performance. Then the conductivity electrode is immersed
in the suspension and the electrical conductivity is measured.
[0050] The dry-milled ATH particles can also be characterized as
having a soluble soda content of less than about 0.1 wt. %, based
on the dry-milled ATH particles. In other embodiments, the
dry-milled ATH particles can be further characterized as having a
soluble soda content in the range of from greater than about 0.001
to about 0.1 wt. %, in some embodiments in the range of from about
0.02 to about 0.1 wt. %, both based on the dry-milled ATH
particles. While in other embodiments, the dry-milled ATH particles
can be further characterized as having a soluble soda content in
the range of from about 0.001 to less than 0.03 wt %, in some
embodiments in the range of from about 0.001 to less than 0.04 wt
%, in other embodiments in the range of from about 0.001 to less
than 0.02 wt %, all on the same basis. The soluble soda content can
be measured according to the procedure outlined above.
[0051] The dry-milled ATH particles can be, and preferably are,
characterized by the non-soluble soda content. While empirical
evidence indicates that the thermal stability of an ATH is linked
to the total soda content of the ATH, the inventors hereof have
discovered and believe, while not wishing to be bound by theory,
that the improved thermal stability of the dry-milled ATH particles
produced by the process of the present invention is linked to the
non-soluble soda content. The non-soluble soda content of the
dry-milled ATH particles of the present invention is typically in
the range of from about 70 to about 99.8% of the total soda content
of the dry-milled ATH, with the remainder being soluble soda. In
some embodiments of the present invention, the total soda content
of the dry-milled ATH particles is typically in the range of less
than about 0.20 wt. %, based on the dry-milled ATH, preferably in
the range of less than about 0.18 wt.%, based on the dry-milled
ATH, more preferably in the range of less than about 0.12 wt. %, on
the same basis. In other embodiments of the present invention, the
total soda content of the dry-milled ATH particles is typically in
the range of less than about 0.30 wt. %, based on the dry-milled
ATH, preferably in the range of less than about 0.25 wt. %, based
on the dry-milled ATH, more preferably in the range of less than
about 0.20 wt. %, on the same basis. In still other embodiments of
the present invention, the total soda content of the dry-milled ATH
particles is typically in the range of less than about 0.40 wt. %,
based on the dry-milled ATH, preferably in the range of less than
about 0.30 wt. %, based on the dry-milled ATH, more preferably in
the range of less than about 0.25 wt. %, on the same basis.
Use of the Dry-Milled ATH
[0052] The dry-milled ATH particles according to the present
invention can be used as a flame retardant in a variety of
synthetic resins. Thus, in one embodiment, the present invention
relates to a flame retarded polymer formulation comprising at least
one synthetic resin, in some embodiments only one, and a flame
retarding amount of dry-milled ATH particles according to the
present invention, and molded and/or extruded articles made from
the flame retarded polymer formulation.
[0053] By a flame retarding amount of the dry-milled ATH particles,
it is generally meant in the range of from about 5 wt % to about 90
wt %, based on the weight of the flame retarded polymer
formulation, preferably in the range of from about 20 wt % to about
70 wt %, on the same basis. In a most preferred embodiment, a flame
retarding amount is in the range of from about 30 wt % to about 65
wt % of the dry-milled ATH particles, on the same basis. Thus, the
flame retarded polymer formulation typically comprises in the range
of from about 10 to about 95 wt. % of the at least one synthetic
resin, based on the weight of the flame retarded polymer
formulation, preferably in the range of from about 30 to about 40
wt. % of the flame retarded polymer formulation, more preferably in
the range of from about 35 to about 70 wt. % of the at least one
synthetic resin, all on the same basis.
[0054] Non-limiting examples of thermoplastic resins where the ATH
particles find use include polyethylene, ethylene-propylene
copolymer, polymers and copolymers of C.sub.2 to C.sub.8 olefins
(.alpha.-olefin) such as polybutene, poly(4-methylpentene-1) or the
like, copolymers of these olefins and diene, ethylene-acrylate
copolymer, polystyrene, ABS resin, AAS resin, AS resin, MBS resin,
ethylene-vinyl chloride copolymer resin, ethylene-vinyl acetate
copolymer resin, ethylene-vinyl chloride-vinyl acetate graft
polymer resin, vinylidene chloride, polyvinyl chloride, chlorinated
polyethylene, vinyl chloride-propylene copolymer, vinyl acetate
resin, phenoxy resin, and the like. Further examples of suitable
synthetic resins include thermosetting resins such as epoxy resin,
phenol resin, melamine resin, unsaturated polyester resin, alkyd
resin and urea resin and natural or synthetic rubbers such as EPDM,
butyl rubber, isoprene rubber, SBR, NIR, urethane rubber,
polybutadiene rubber, acrylic rubber, silicone rubber,
fluoro-elastomer, NBR and chloro-sulfonated polyethylene are also
included. Further included are polymeric suspensions (latices).
[0055] Preferably, the synthetic resin is a polyethylene-based
resins such as high-density polyethylene, low-density polyethylene,
linear low-density polyethylene, ultra low-density polyethylene,
EVA (ethylene-vinyl acetate resin), EEA (ethylene-ethyl acrylate
resin), EMA (ethylene-methyl acrylate copolymer resin), EAA
(ethylene-acrylic acid copolymer resin) and ultra high molecular
weight polyethylene; and polymers and copolymers of C.sub.2 to
C.sub.8 olefins (.alpha.-olefin) such as polybutene and
poly(4-methylpentene-1), polyvinyl chloride and rubbers. In a more
preferred embodiment, the synthetic resin is a polyethylene-based
resin.
[0056] The flame retarded polymer formulation can also contain
other additives commonly used in the art. Non-limiting examples of
other additives that are suitable for use in the flame retarded
polymer formulations of the present invention include extrusion
aids such as polyethylene waxes, Si-based extrusion aids, fatty
acids; coupling agents such as amino-, vinyl- or alkyl silanes or
maleic acid grafted polymers; barium stearate or calcium sterate;
organoperoxides; dyes; pigments; fillers; blowing agents;
deodorants; thermal stabilizers; antioxidants; antistatic agents;
reinforcing agents; metal scavengers or deactivators; impact
modifiers; processing aids; mold release aids, lubricants;
anti-blocking agents; other flame retardants UV stabilizers;
plasticizers; flow aids; and the like. If desired, nucleating
agents such as calcium silicate or indigo can be included in the
flame retarded polymer formulations also. The proportions of the
other optional additives are conventional and can be varied to suit
the needs of any given situation.
[0057] The methods of incorporation and addition of the components
of the flame-retarded polymer formulation and the method by which
the molding is conducted is not critical to the present invention
and can be any known in the art so long as the method selected
involves uniform mixing and molding. For example, each of the above
components, and optional additives if used, can be mixed using a
Buss Ko-kneader, internal mixers, Farrel continuous mixers or twin
screw extruders or in some cases also single screw extruders or two
roll mills, and then the flame retarded polymer formulation molded
in a subsequent processing step. Further, the molded article of the
flame-retardant polymer formulation may be used after fabrication
for applications such as stretch processing, emboss processing,
coating, printing, plating, perforation or cutting. The kneaded
mixture can also be inflation-molded, injection-molded,
extrusion-molded, blow-molded, press-molded, rotation-molded or
calender-molded.
[0058] In the case of an extruded article, any extrusion technique
known to be effective with the synthetic resin(s) used in the flame
retarded polymer formulation can be employed. In one exemplary
technique, the synthetic resin, dry-milled ATH particles, and
optional components, if chosen, are compounded in a compounding
machine to form the flame-retardant resin formulation. The
flame-retardant resin formulation is then heated to a molten state
in an extruder, and the molten flame-retardant resin formulation is
then extruded through a selected die to form an extruded article or
to coat for example a metal wire or a glass fiber used for data
transmission.
[0059] In some embodiments, the synthetic resin is selected from
epoxy resins, novolac resins, phosphorous containing resins like
DOPO, brominated epoxy resins, unsaturated polyester resins and
vinyl esters. In this embodiment, a flame retarding amount of
dry-milled ATH particles is in the range of from about 5 to about
200 parts per hundred resins ("phr") of the ATH. In preferred
embodiments, the flame retarded formulation comprises from about 15
to about 100 phr preferably from about 15 to about 75 phr, more
preferably from about 20 to about 55 phr, of the dry-milled ATH
particles. In this embodiment, the flame retarded polymer
formulation can also contain other additives commonly used in the
art with these particular resins. Non-limiting examples of other
additives that are suitable for use in this flame retarded polymer
formulation include other flame retardants based e.g. on bromine,
phosphorous or nitrogen; solvents, curing agents like hardeners or
accelerators, dispersing agents or phosphorous compounds, fine
silica, clay or talc. The proportions of the other optional
additives are conventional and can be varied to suit the needs of
any given situation. The preferred methods of incorporation and
addition of the components of this flame retarded polymer
formulation is by high shear mixing. For example, by using shearing
a head mixer manufactured for example by the Silverson Company.
Further processing of the resin-filler mix to the "prepreg" stage
and then to the cured laminate is common state of the art and
described in the literature, for example in the "Handbook of
Epoxide Resins", published by the McGraw-Hill Book Company, which
is incorporated herein in its entirety by reference.
[0060] The above description is directed to several embodiments of
the present invention. Those skilled in the art will recognize that
other means, which are equally effective, could be devised for
carrying out the spirit of this invention. It should also be noted
that preferred embodiments of the present invention contemplate
that all ranges discussed herein include ranges from any lower
amount to any higher amount. For example, when discussing the oil
absorption of the dry-milled ATH, it is contemplated that ranges
from about 30% to about 32%, about 19% to about 25%, about 21% to
about 27%, etc. are within the scope of the present invention.
* * * * *